The present invention relates to a heating amount adjusting device for a preheater used in a corrugated cardboard producing machine.
In general, a corrugated cardboard producing machine operates as follows. As shown in FIG. 9, an original paper 2 fed out of a mill roll stand 1 is supplied as a liner paper to a single facer 5 through a splicer 3 and a preheater for paper splicing. On the other hand, an original paper 9 is fed as a central core paper from another mill roll stand 6 to the single facer 5 through a splicer 7 and a preconditioner 8 for wetting and adjusting a humidity. In the single facer 5, the original paper 9 is corrugated and formed into the central core paper, and the original paper 2 for the above-described liner paper is attached to the central core paper, thereby producing a single face corrugated cardboard sheet 10, i.e., a one-sided corrugated cardboard. In the corrugated cardboard producing machine, there is provided another producing system 12 having the same structure as that of the foregoing system for producing a corrugated cardboard sheet 11. The respective corrugated cardboard sheets 10 and 11 of the single face type are bonded together through an overhead bridge conveyor 13, a preheater 14 and a gluing machine 15. In addition, a liner paper 16 is also bonded to the corrugated cardboard sheets, to thereby produce a double face type corrugated cardboard sheet, i.e., a so called two-sided corrugated cardboard sheet. This double-face corrugated cardboard sheet will be subjected to various processes such as a folding or turning line formation by using a slitter scorer and will be cut into a predetermined length.
As described above, the preheaters 4 and 14 and the preconditioners 8 are interposed in predetermined positions of the corrugated cardboard producing machine. As shown in FIG. 10, each of the preheaters 4 and 14 and the preheater portions of the preconditioners 8 are structured to supply a steam into a cylindrical roll 17 which is drivingly rotated, thereby heating the interior of the roll 17. Since it is difficult to adjust the heat amount of the roll 17, i.e., the temperature thereof by the supply amount of the steam, a contact length, i.e., a lap amount with the respective single face type cardboard sheets 10 and 11 or the original papers 2 and 9 is adjusted. In other words, large diameter gears 19 and 20 are rotatably mounted on bearing portions of the roll 17 relative to a frame 18, and an adjusting roll 21 is pivoted to the respective gears 19 and 20. The respective gears 19 and 20 are engaged with gears 22 and 23. A rotary shaft 24 of the gears 22 and 23 is connected to a motor 27 through a worm gear 25 and a worm 26. Then, as shown in FIG. 11, the adjusting roll 21 is moved along the outer circumference of the roll 17 by rotating the gears 19 and 20 using the motor 27, to thereby change the lap amount between the roll 17 and the original paper 2, 9 or the single face type corrugated cardboard sheet 10, 11 in accordance with the conditions such as a thickness and a paper quality of the original paper 2, 9 or the single face type corrugated cardboard sheet 10, 11. Thus, the heating amount of the original paper 2, 9 or the single face type corrugated cardboard sheet 10, 11 is set. It is also noted that the preconditioner 8 includes the unit for providing a moisture as well as the above-described heater.
However, in each of the foregoing conventional preheaters 4, 14 and preheater portions of the preconditioners 8, if the adjusting roll 21 is angularly moved in order to change the lap amount with each of the original papers 2, 9 or the single face type corrugated cardboard sheets 10, 11, as is apparent from FIG. 11, a length of the original papers 2, 9 or the single face type corrugated cardboard sheets 10, 11 from guide rolls 28 on the introduction side to the adjusting roll 21 is changed. On the other hand, the recent corrugated cardboard producing machine as a whole is automated by computers. Accordingly, if the length of the original papers 2, 9 and the single face type corrugated cardboard sheets 10, 11 is changed in the preheaters 4, 14 and the preconditioners 8 as described above, a stagnant length is changed as the original papers or the like are stagnant and conveyed on the overhead bridge conveyor 13 in a corrugated and curved manner. The change of the stagnant length causes an error in final production length when a lot changing operation is effected by an order change. For this reason, in the prior art, the angular movement range of the adjusting roll 21 is divided into four parts. In accordance with the situation as to whether or not the adjusting roll 21 for the above-described lap amount falls within any one of the four-divided parts, a suitable correction value substantially corresponds to the length of the original papers 2, 9 or the single face type corrugated cardboard sheets 10, 11 which are changed within the preheaters 4, 14 and the preconditioners 8. The correction value is inputted into the subsequent devices for control. Since the correction value is set only at one of the four parts, the value is rough. Accordingly, if the various devices are controlled in accordance with the correction value, the resultant control involves a large error.
Furthermore, if the stagnant length of the original papers 2, 9 or the single face type corrugated cardboard sheets 10, 11 is changed in correspondence with the lap amount in the preheaters 4, 14 and the preconditioners 8, a tension of the original papers 2, 9 or the single face type corrugated cardboard sheets 10, 11 is also changed. As a result, a position of a dancer roll provided in the splicer 3 or 7 is changed so that the stagnant length within the splicer 3 or 7 which would be inherently controlled as a constant value is changed, and so that as described above, a further error is generated in the final production length. It is also difficult to incorporate, into a softwear of a production control system (not shown) for controlling the subsequent devices such as the overhead bridge conveyor 13, the correcion value representative of any undue length change of the original papers 2, 9 or the single face type corrugated cardboard sheets 10, 11 within the splicers 3, 7.